Project Summary/Abstract Background: Transcriptional mechanisms that regulate epidermal homeostasis have been well established but recently we have discovered that post-transcriptional mechanisms play prominent roles in maintaining epidermal self-renewal. We have shown that the RNA helicase DDX6 is necessary to maintain epidermal self-renewal through the mRNA degradation and translation pathway. By associating with specific members of the translation pathway DDX6 binds to and mediates the translation of self- renewal and proliferation transcripts to maintain self-renewal. DDX6 also associates with mRNA degradation proteins to bind differentiation-inducing transcripts to promote their degradation to prevent premature differentiation. Objective/hypothesis: This proposal seeks to understand the regulation of epidermal homeostasis and tumor initiation through post-transcriptional mechanisms. We previously identified proteins associated with DDX6 and our objective is to characterize the role of each protein in regulating epidermal growth, differentiation, and progression to neoplasia as well as the mechanisms of action. Furthermore we seek to determine the specific transcripts that DDX6 and its associated complexes bind during homeostasis and tumor initiation. Specific Aims: (1) To determine the role of DDX6 associated proteins on epidermal homeostasis and tumor initiation and (2) to identify and characterize the transcripts associated with DDX6 complexes. Study Design: To study epidermal homeostasis in a more clinically relevant setting, we generate 3-dimensionally intact human skin, containing human epidermal cells (that have been permanently knocked down for either DDX6 or its associated proteins) in the context of human dermal stroma and basement membrane, regenerated on immune compromised mice. By using this model, we can perform loss of function experiments on DDX6 and its associated proteins in regenerated human skin to characterize their role in epidermal growth, differentiation, and progression to neoplasia. We will also use CLIP- Seq to determine the RNAs associated with DDX6 complexes during the progression from normal to neoplastic epidermis.